This invention relates generally to structures employing thin film materials and relates, more particularly, to electronic devices and structures which utilize thin film ferroelectric materials.
The class of structures with which this invention is to be compared includes tunneling structures which include two conducting electrodes and a ferroelectric layer sandwiched between the two conducting layers. A remanent polarization can be induced within the ferroelectric layer (i.e. below the Curie temperature of the ferroelectric layer) so that the ferroelectric layer provides a barrier to electron flow unless a voltage difference which is greater than a threshold voltage is applied across the electrodes. An example of such a tunneling structure is shown and described in U.S. Pat. No. 5,541,422.
Heretofore, the development of structures such as that described in the referenced patent have focused primarily upon the ferroelectric layer, as opposed to the electrodes, for the control of the electron transport behavior within the structure. It would be desirable to provide a tunneling structure of the aforedescribed class whose transport behavior can be effected or controlled by techniques other than through the selection or build up of the ferroelectric layer.
Accordingly, it is an object of the present invention to provide a new and improved tunneling element of the aforedescribed class whose transport behavior is advantageously affected by means other than through the selection or construction of the ferroelectric layer.
Another object of the present invention is to provide such an element which is particularly well-suited for use in memory structures employing relatively simple architecture and can reduce the volatility-related limitations associated with current memory chips and provide fast access times.
Yet another object of the present invention is to provide such an element which, when incorporated within a memory device, advantageously effects the ultimate scalability of the memory device and accommodates fast access times generic for all ferroelectric memories.
A further object of the present invention is to provide a memory device which utilizes the new and improved tunneling element.
A yet further object of the present invention is to provide such a structure which is uncomplicated in structure, yet effective in operation.